"Using a Browser with Dev Tools to Debug a Web Application" matching MCP connectors:

Free platform to test MCP clients without installing anything. Create mock tools with dynamic templates, configurable delays, conditions (if/then), and response sequences. Supports JSON-RPC 2.0 over Streamable HTTP. Built-in text_echo and json_echo tools. Rate-limited tiers: anonymous (5 calls/min, 1 mock tool), registered (10 calls/min, 4 mock tools), premium (60 calls/min, unlimited). Zero setup — no install, no registration required. More info: https://www.testmcp.dev

Point Gecko at an OpenAPI spec; get first-call-correct, auth-hidden agent tools.

Your DRF API as MCP tools — 1,800 endpoints become 16 dispatchers, permissioned by Django.

Apideck Unified API MCP — 330 tools across 200+ SaaS connectors (accounting, CRM, HRIS, ATS).

A webhook inbox for agents: one call returns a live URL. Mock, verify, inspect and replay.

Deterministic JSON checks with signed evidence and x402-paid execution

Check an MCP endpoint resolves: liveness, live tool list, schema drift. Free.

Create hosted mock REST APIs as tools: seed fake data, import specs, query, write, snapshot. Free.

Instant no-signup webhook & HTTP-request inspector for testing webhooks and agent tool-callbacks.

httpbin echo: GET/POST inspection, status codes, delay, UUID, base64. Debug aid.

Deterministic validation for AI-generated artifacts: JSON Schema, OpenAPI response, SQL syntax.

Debug webhooks from your AI agent: inspect and replay captured webhooks on localhost.

Unified gateway exposing 150+ tools across all NexGenData MCP servers via one endpoint.

End-to-end API testing — generate and run tests from OpenAPI, curl, Postman, or real user traffic.

MCP server that delivers up-to-date Bitrix24 REST API documentation.

An MCP server that provides tools to validate an email address using Dilli Email Validation API.

40+ developer tools from Context7, Code Runner, Python Execute, NPM Sentinel, PlantUML, and Microsoft Learn. Docs lookup, code execution, security scanning. Starts at $0.01/call. Get your API key at app.xpay.sh or xpay.tools

Public benchmark where agents submit Q&A answers and get scored on a leaderboard.

Conformance checker for MCP servers. Free, no key, verdicts recomputable and re-measured daily.

MCP server for AI access to SmartBear tools, including BugSnag, Reflect, Swagger, PactFlow, QTM4J.